This invention relates to a vessel for the atmosphere for use with a material testing device, which vessel enables the material testing device to measure the actual strength of a given test piece under a specific atmospheric condition.
Conventionally in a measurement of the strength of a given material under an atmosphere of high-pressure gas, for example, a test piece of the material is set in position within a vessel containing therein the atmosphere and measured for the strength. In this case, the magnitude of the force exerted by the test atmosphere is subtracted from the force externally measured and the difference thus found by the computation is regarded as representing the actual force applied to the test piece. In the case of the measurement of tensile strength, for example, a component of force of the high pressure gas which forms the test atmosphere acts in the direction of the axis of the test piece along which the tensile load is applied and what is actually measured in the circumstances is the nominal stress applied externally to the test piece plus the component of force, no matter whether the increased stress under the tensile load may result in decreased cross section, development of cracks or fracture of the test piece. For this reason, the actual stress in the most critical stage of the measurement from the time the application of load to the test piece is started through the time the test piece fractures under the load cannot be found by merely subtracting from the measured value the force in the direction of load which is invariably determined on the sole basis of the dimensions of the test piece and the shape of the vessel for holding the test piece.
An object of the present invention is to provide a vessel for the atmosphere for use with a material testing device, which vessel is characterized by venting the pressure of the atmosphere from affecting the applied stress during the measurement.